The "Drop-In"
Residential Heat Pump Water Heater

A market-driven solution to efficient
electric heating

The Problem: How to Convince Consumers to Save Energy
in Water Heating

About half of all domestic water heating is done with electric
resistance storage water heaters. The most efficient resistance
water heater has an energy factor (EF) of 0.95, only 5% below the
maximum efficiency possible for that type of water heater. Yet by
using electricity to "pump heat" from the surrounding
space, the residential heat pump water heater (HPWH) can attain
much higher efficiencies, reducing the electricity needed for
water heating by at least half.

Despite such high efficiencies, today's U.S. market for
residential HPWHs is small and stagnant (less than 2,000
units/year) and is served by only two or three manufacturers.

Why has the HPWH market remained small? Assessments conducted
by DOE and others point to a number of issues:

Economics  High first cost, leading to long payback
time.

Reliability  Failures of early models created a
poor reputation for the HPWH.

Awareness  Customers not aware of HPWH benefits;
few have even seen one.

The Solution: The "Drop-in" HPWH

Building from a strong understanding of these technical and
market issues, Enviromaster International (EMI) and Arthur D.
Little, with support from the DOE ENERGY STAR Program through Oak
Ridge National Laboratory, are developing a unique
"market-optimized" ambient-air HPWH aimed at the large
electric water heater replacement market.

Design Features

A full "drop-in" replacement for 50- or
80-gallon electric water heater  same footprint as
the original water heater, an identical electrical
hookup, no need for additional plumbing, and no
condensate drain required

HPWH uses a small, ducted evaporator
fan; noise not expected to be an issue

Hot water runouts minimized

At least one resistance element will
be retained in the final design to meet unusually heavy
draws; both elements will be retained in field test
trials

National Field Testing and Demonstration

National field testing is scheduled to begin in FY 1999 with
participation by selected utilities. The utilities will identify
two or three test homes, install HPWH and monitoring
instrumentation, administer participant surveys, remove or
replace water heat at conclusion of the experiment, and assist
DOE in follow-on demonstration and promotion activities.

EMI will provide HPWHs for the field test, maintain and repair
the units, implement design improvements on the basis of field
tests results, obtain product certification and approval, and
develop product support materials (installation instructions,
maintenance, etc.).

DOE will develop field test criteria, protocol, and coordinate
overall testing; provide the instrumentation for utility
installation; collect and analyze the data and share it with the
utility participants; provide performance data and analysis to
EMI; initiate follow-on field demonstration and promotion under
DOE ENERGY STAR Program; and draft installation guidelines and
performance predictions to support marketing efforts.

Following this initial field test, a larger field
demonstration and promotion effort will be conducted. This will
include open utility participation with 200300 HPWH units
and selected monitoring in partnership with the utilities. It is
anticipated that the HPWH will be launched commercially in 2000.